<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
      .active {
          color: red;
      }
  </style>
</head>
<body>

<script src="../js/vue.js"></script>
<div id="app">
  <ul>
    <li v-for="(item,index) in moives"
        v-on:click="changeClass(index+1)"
        v-bind:class="{active:currentIndex==index+1}">{{item}}</li>
  </ul>
</div>

<script>
  const app = new Vue({
    el: '#app',
    data: {
      moives: ['海王', '复仇者联盟', '黑寡妇', '大话西游'],
      currentIndex:0
    },
    methods: {
      changeClass: function (index) {
        this.currentIndex = index;
      }
    }
  })
</script>

</body>
</html>